L1 mice lack spinal cord potentiation. (A) Number of spikes elicited by A-fiber intensity stimuli before and after administration of a C-fiber specific conditioning stimulus consisting of 240 shocks (200 μA, 200 μs at 2 Hz). Wild type (wt) (n = 5) mice developed a large and significant increase (One-way ANOVA, Bonferroni post-test, P < 0.01), whereas L1 (n = 6) mice did not show any change in the number of elicited spikes. (B) Representative original recordings obtained from wild type (wt) and L1 mice before and 2 h after C-fiber conditioning. Bottom panel, shows a representative original recording of the absence of potentiation in wild type mice 2 h after A-fiber conditioning. (C and D) Number of spikes in ventral roots by graded dorsal root stimulation immediately before (Preconditioning) and 2 h after conditioning (Postconditioning), obtained from wild type (wt) (n = 5) and L1 (n = 6) mice.